ReaxFF EC molecule disintegration

Dear Users,

I am currently learning to use the ReaxFF forcefield in the simulation of Ethylene Carbonate molecules using LAMMPS. I am trying to reproduce results from this research paper. However, when I try to run a basic simulation with 4 replicated ethylene carbonate molecules using the following input script, I find that the molecules explode into atoms and sometimes form unphysical structures (more than two bonds for H, 3 for O, etc.).


units real
dimension 3
boundary p p p
atom_style charge

Atom Definition

dump dumpXYZ all xyz 100 mydump.EC
replicate 2 2 2

Defining ReaxFF style/coeff

pair_style reax/c NULL checkqeq yes enobonds yes
pair_coeff * * H C O


neigh_modify delay 0 every 1 check yes

#velocity all create 298.15 4928459 rot yes mom yes dist gaussian

fix 1 all nve
fix 2 all qeq/reax 1 0.0 10.0 1e-6 reax/c #param.qeq
fix 3 all temp/berendsen 10 10 50.0

#Write data file for test

timestep 0.01


thermo_style one
thermo 100

Run the simulation

run 100000

I also receive this warning, “VdWaals-parameters for element O indicate inner wall+shielding, but earlier atoms indicate different vdWaals-method. This may cause division-by-zero errors. Keeping vdWaals-setting for earlier atoms. (src/USER-REAXC/reaxc_ffield.cpp:259)”

However, I have tested with other applicable reaxFF files, and these result in the same disintegration of the molecules as well (without getting the above warning), which leads me to believe that it is to do with the input script. I have also tried with/out having a velocity defined, thermostat at different temperatures, and using a single molecule as well with the same result.

Any suggestion/s to overcome this issue is most welcome.

Thank you for your time.

Don Peiris

output.text (145 KB) (471 Bytes) (12 KB)

you have a bad data file. it has the types for carbon and hydrogen
atoms swapped. no surprise that they want to rearrange the geometry.